One major problem you will encounter when
setting up an electronic-imaging station is
interconnecting the various components that make up
the imaging system. The technology in each
component area is developing at a rapid rate. With the
ever-increasing number of hardware components and
software packages available on the market, setting up
the links between the devices can become frustrating.
Before choosing new components for a system, you
must look carefully at each piece of new equipment to
be sure it is compatible with the existing system.
INPUT
Several ways to acquire photographs electronically
are used. You can obtain these photographs from digital
or still-video cameras, or you can scan and digitize
existing film and paper images.
Before a computer with the appropriate software
can be used to modify or enhance an image, the image
must be converted to digital values. Images that are
imported from a still-video camera are in analog
waveform. An analog waveform is a value that varies
continuously over time (fig. 3-4). For an analog
waveform to become a digital signal, both the value and
the time must be changed into noncontinuous, numeric
values of ones and zeros (fig. 3-5). The process used to
determine time is called sampling. Sampling is done at
equal increments of time. Conversion of continuous
values into distinct values is called QUANTITIZING.
The combined process is called analog-to-digital
conversion (A/D conversion) or DIGITIZING.
The A/D conversion process is an approximation.
When the sampling rate is low, a very inaccurate
representation of the signal results. When the sampling
rate is high, virtually an exact copy of the original signal
is attained. When color images are digitized, the red,
green, and blue information is handled as three separate
sets of data to produce three sets of digital information.
Figure 3-4.—Analog waveform.
Figure 3-5.—Digital signal.
In this case, three A/D circuits are used and the encoding
is done simultaneously.
When an image is digitized, a series of points are
created. These points are called pixels. When the
resolution of the display system is low, the individual
pixels may be noticeable. This objectionable resolution
is called pixelation.
Electronic Still Cameras
The advantage of using a digital or still-video
camera is the image may be captured and inputed to the
electronic-imaging workstation instantly. The features
on these cameras are basically the same, and they are
used in the same manner as conventional cameras. The
features of conventional cameras and electronic
cameras that are similar are as follows:
The lenses may be fixed or interchangeable,
depending on the camera.
The lenses are identified by f/stops and focal
length.
The focusing may be fixed, automatic, or
manual, depending on the camera.
The range of shutter speeds is similar.
The flash may be built-in or have a dedicated
hot shoe.
Each electronic camera has an image sensor. The
image sensor, called the “charge-coupled device”
(CCD), is the main component of an electronic camera.
The CCD is rated in size, pixels, and ISO. The larger
the CCD, the more pixels it can record, thus the higher
the resolution. However, the resolution quality and the
exposure range of an electronic camera is not as great
as what can be achieved with film.
3-8
